Latent TGF beta 1 cDNA encodes a 390 amino acid precursor that contains a 29 aa signal peptide and a 361 aa proprotein. A furin?like convertase processes the proprotein to generate an N?terminal 249 aa latency?associated peptide (LAP) and a C?terminal 112 aa mature TGF? beta 1. Disulfide?linked homodimers of LAP and TGF? beta 1 remain non?covalently associated after secretion, forming the small latent TGF? beta 1 complex.